Add config method

Signed-off-by: Rahul Rudragoudar <rr83019@gmail.com>

src/main/scala/lc/captchas/FilterChallenge.scala

@@ -10,6 +10,11 @@ import lc.captchas.interfaces.Challenge
 
 class FilterChallenge extends ChallengeProvider {
   def getId = "FilterChallenge"
+
+  def configure(config: String): Unit = {
+    // TODO: add custom config
+  }
+
   def returnChallenge(): Challenge = {
     val filterTypes = List(new FilterType1, new FilterType2)
     val r = new scala.util.Random

src/main/scala/lc/captchas/LabelCaptcha.scala

@@ -23,6 +23,10 @@ class LabelCaptcha extends ChallengeProvider {
 
   def getId = "LabelCaptcha"
 
+  def configure(config: String): Unit = {
+    // TODO: add custom config
+  }
+
   def returnChallenge(): Challenge =
     synchronized {
       val r = scala.util.Random.nextInt(knownFiles.length)

src/main/scala/lc/captchas/RainDropsCaptcha.scala

@@ -31,6 +31,10 @@ class RainDropsCP extends ChallengeProvider {
 
   def getId = "FilterChallenge"
 
+  def configure(config: String): Unit = {
+    // TODO: add custom config
+  }
+
   private def extendDrops(drops: Array[Drop], steps: Int, xOffset: Int) = {
     drops.map(d => {
       val nd = new Drop()